4.9 Fundamentals of Communication and Networking Flashcards
1
Q
Baud Rate
A
The number of signals sent per second
2
Q
Bit Rate
A
The rate at which bits are transferred
Bit rate >/ baud rate
3
Q
Bandwidth
A
The capacity of wired/wireless network communications
4
Q
Latency
A
The delay between transfer of data and seeing the result of that instruction
5
Q
Protocol
A
Set of rules for data exchange across a network
6
Q
Serial (2)
A
- one bit transmitted at once down one wire
- external distances
7
Q
Parallel (2)
A
- multiple bits sent at once using multiple wires
- internal distances
8
Q
Serial (Adv: 3, Dis: 1)
A
Adv
- simple set up
- cheap
- reliable
Dis
- slow transmission
9
Q
Parallel (Adv: 1, Dis: 2)
A
Adv
- faster transmission
Dis
- less reliable (skew due to interference)
- expensive
10
Q
Synchronous Transmission (5)
A
- data sent at regular intervals
- synchronised by clock signal
- clock pulse shared by receiver and sender
- helps with skew so used in parallel
- used for reliable, time sensitive data
11
Q
Asynchronous Transmission (2)
A
- bytes sent as soon as they’re ready
- parity, start, stop
12
Q
Bus Topology (2)
A
- one cable: backbone
- terminator at end of cable that reflects signal
13
Q
Bus Topology (Adv: 3, Dis: 3)
A
Adv
- cheaper to install (less cables)
- no additional hardware
- easy to add nodes
Dis
- poor security
- main cable fail
- performance decreases heavily with traffic
14
Q
Star Topology (1)
A
- each device has own cable connected to switch/hub
15
Q
Star Topology (Adv: 5, Dis: 2)
A
Adv
- easy to add
- consistent performance despite traffic
- more secure
- easy to isolate faults (single cable fails)
- no collisions
Dis
- central node goes down
- expensive to set up
16
Q
Client-Server (1, Adv:2, Dis:1)
A
- all data stored on dedicated server
- adv: centralised security/backups, files/software stored securely on server
- dis: server goes down
17
Q
Peer-To-Peer (1, Adv:2, Dis:1)
A
- all devices have equal status
- adv: no specialised hardware, node goes down
- dis: no centralised security/backups/management
18
Q
LANs and WANs Advantages (4)
A
- cheap, easy communication
- share files/hardware
- centralised file storage/install/update/back up
- log in from any device
19
Q
WiFi (Def, 2)
A
- WiFi is a wireless LAN based on international standards
- slower and less reliable than ethernet
- Hot spots = public WiFi
20
Q
NIC/Wireless Network Adaptor (4)
A
- Located in device
- Allows device to connect to wireless system
- Allows device to communicate by sending and receiving data
- Assigns MAC address
21
Q
WAP (3)
A
- Located in router
- Allows wireless devices to connect to wired network
- Assigns IP address
22
Q
Network Security (5)
A
- Doesn’t stop allowed user from using malware
- Protects against unauthorised access
- WPA/WPA2 -WiFi Protected Access
- Authentication, encryption, passwords
- SSID - Service Set Identifier
- Unique number to identify a network
- Must use same number to join network
- Turn off broadcasting (only those who know exist + password can join)
- MAC Address white list
- List of users (MAC addresses) who can access network
23
Q
Firewalls (7)
A
- A system that filters network traffic to protect against unauthorised flows of data in/out of a network
- Hardware or software
- Isolates network traffic
- Allows/denies based on IP address
- Packet Filtering
- Checks packet header to see if source/destination addresses are allowed/denied
- Stateful Packet Inspection:
- Looks at data inside packet
- If any common warning signs, packet is stopped from progressing
- Packet only allowed if passes both
24
Q
Proxy Servers (4)
A
- Act as ‘middle man’ between client and webserver
- Client ←→ Proxy Server ←→ Web Server
- Once obtained from web, copy of data stored on proxy server
- After while, proxy server sends data back to web server to free up space
25
Malware (def)
Software created with intention to cause harm
Corrupts and compromises data
26
Viruses (6)
- Attaches itself to program/file, by making copy of itself
- enabling it to spread from one device to another
- Typically executable files
- Means cannot spread without human interaction
- Spread through lack of awareness
- Exploits same vulnerabilities as worms
27
Worms (5)
- Similar to viruses in design
- Doesn’t need human interaction to spread
- Automatically self replicates
- - Automatically sends itself to everyone in address book via email
- Exploits out of date systems - no security updates
28
Trojans (5)
- Appear genuine but have hidden agenda
- Attached to executable file
- Create backdoors which malicious users can exploit
- Doesn’t spread, self-replicate, cause harm
- Exploits lack of understanding and systems with out of date anti virus software
29
Symmetric Encryption (4)
- One key for both
- Key exchanged through secured channels
- Easy decoded
- e.g. caesar, vernam
30
Asymmetric Encryption (keys)
Public key = encrypt
Private key = decrypt
Extremely secure
31
Digital Certificates (4)
- Unique code to verify your identity
- Ensures encrypted message from trusted source
- Contains name, ID, public key, signature
- Awarded by a certification authority (trusted organisation)
32
Digital Signatures (2)
- Similar to real life signature
- Uses mathematical functions + keys to create unique signature
33
Digital Signatures Used for (2)
- Message has not been corrupted
- Sender is who they say they are
34
Digital Signatures - Sending Messages
- Hash plaintext message → message digest
- Sender private key + digest → signature
- Signature + plaintext message
- Encrypt using receiver’s public key
- Send message
- Decrypt using receiver’s private key
- Split signature and plaintext message
- Sender’s public key + signature → digest
- Rehash plaintext → message digest
- Compare two digests to see if the same
35
MAC vs IP (5)
MAC
- LAN based
- Hex
- Static
- Completely Unique
- Assigned by NIC
IP
- WAN based
- Binary/Denary
- Dynamic
- Unique within Network
- Assigned by router
36
IP Addresses (Purpose, Parts, 2)
Purpose = “To identify a device on a network using a unique number”
2 Parts:
- Network identifier (number of bits varies)
- Host (device) identifier
Largest IP address: 255.255.255.255
IPv6: 6 sections not 4, hex not binary
37
Subnets (def, 2, eq)
- Smaller part of a larger network
- More efficient & secure transmission (reduces collisions/devices passed through)
- Can send data directly without router
- Check if devices on the same network
- - Mask AND sender IP = mask AND receiver IP (gives NetworkID)
- - Number of 1s as designated to ID
38
Public vs Private IP (2)
Private = cannot be accessed outside of network (non-routable)
Public = needed to route over internet
39
Data Packet Structure (3)
Header: packet size, packet number, protocol, destination and sender address, protocol identifier, port number, check sum (error checking method)
Body: Actual data of the packets
Footer: Tell receiver end of packet reached
40
Packet Switching (5)
- More secure and efficient
- TCP splits into multiple packets
- IP routes individual packets into different directions (travel through fastest route)
- TCP checks transmission was successful
- TCP sequences packets back inro correct order at destination
41
Layers (2)
- Reduces complexity of networking
- Each layer accessed & edited separately
42
Application Layer (2)
- Defines TCP/IP protocols & how host programs interface with transfer layer services
- Includes higher level protocols
43
Transport Layer (4)
- Purpose = permit devices on the source and destination host to carry on a conversation
- Defines the level of service and status of the connection used when transporting data
- Breaks data into packets
- Main protocols used: TCP and SSH
44
Network Layer (2)
- Defines how data is physically sent through the network
- Defines how bits are electrically or optically signalled by hardware devices
45
Link Layer (2)
- Handles the moving of data in and out of a physical link in a network
- Used to interconnect hosts/nodes in the network
46
NAT (acronym, 2)
- Network Address Translation
- Responsible for converting IP addresses as they pass over the boundary between public and private addresses space (e.g. via a router)
- Table of requests and IPs
47
CSMA (4)
- Carrier Sense Multiple Access
- Purpose is to provide error free transmission within a LAN
- Checks that all devices & cables are clear and ready to send and receive data
- Helps to prevent the collision of packets
48
CSMA with Collision Avoidance
Without RTC/CS (Request To Send/Clear To Send)
- Assemble a frame
- Check is channel is idle
- If idle : transmit data
- If not: wait for random amount of time and check again
With RTS/CS
- Assemble a frame
- Check is channel is idle
- If idle: send RTS
- - Receiver received RTS
- - Sends back CTS if clear
- - Data transmitted if receiver received CTS
- - If not: wait for random time and check again
- If not: wait for random time and check again
49
DHCP (Acronym, Purpose, Benefit)
- Dynamic Host Configuration Protocol
- Purpose: DHCP server automatically assigns a dynamic IP address to a computer from a pool of available addresses
- Benefit: Takes IP back after use (helps shortage)
50
DHCP Method
- Device sends discovery message
- The DHCP sends an offer out
- The device then sends the request
- The DHCP sends out confirmation
51
TCP/IP (Acronym, 2)
- Transmission Control Protocol/Internet Protocol (TCP/IP)
- Provides error free transmission between 2 devices
- Routes packets on a WAN
52
HTTP (Acronym, 2)
- Hyper-Text Transfer Protocol (HTTP)
- Defines how data from web pages is transferred from server to client
- Client-server method of requesting HTML files
53
SMTP (Acronym, 2)
- Simple Main Transfer Protocol (SMTP)
- Sends mail to a mail server
- Client → mail server
54
POP (Acronym, 3)
- Post Office Protocol (POP)
- Used by email clients to get email from a mail server (receives mail)
- Web server → client
- Have to rerequest as emails deleted once read
55
IMAP (Acronym, 4)
- Internet Message Access Protocol (IMAP)
- Receives: web server → client
- Synchronises: automatic updates
- Used to manage mail boxes
- Messages only deleted when user explicitly requests they are
56
Telnet
Unencrypted = not secure
57
FTP (acronym, 2)
- File Transfer Protocol
- Sending files between computers
- Client software
58
SSH Process
- Client initiates the connection by contacting server (client → server)
- Server sends public key to client (client ← server)
- Server and client agree communication rules and open a secure channel (client ←→ server)
- - May have few passes (may reject and resend new rules)
- User can now login to the remote server host OS (client → server)
59
Web Browsers (Structure 2)
- Head = titles and styling scripts
- Body = main content
60
Web Names (Names, Levels, Use Over)
- Website domain name: craiganddave.org
- Fully qualified domain name: www.craiganddave.org/cryptic.pdf
- Uniform resource locator (URL): https://www.craiganddave.org/cryptic.pdf
- 3rd level e.g. bbc, amazon
- 2nd level e.g. .co, .gov, .ac
- Top level e.g. .com, .org, .net, .uk, .fr
- Use URL over IP as it is easier to remember and to type (less errors)
61
Port Numbers (4*, 5)
20 = FTP data
21 = FTP control instructions
* 22 = SSH remote login
* 23 = Telnet remote login
25 = SMTP
* 80/8080 = HTTP
110 = POP3
143 = IMAP
* 443 = HTTPS
62
Port Forwarding (3)
- A webpage coming back to a network will arrive through a port on the router
- Router sees which device requested that page and forwards it down that specific port
- Allows computers to exchange data directly between each other without need for complex transition step
63
Thick Clients (4)
- Hold the majority of the data
- Need more RAM + decent processor
- Share with other clients that request
- Less reliance on server
64
Thin Clients (3)
- Hold only a small amount of data
- Need less RAM + high bandwidth + very good connection
- Request majority of data from other clients
64
Domain Name Server
- Client sends DN to DNS
- - DN sent to bigger DNS
- - IP address copied to DNS
- DNS looks up corresponding IP + sends to client
- - Error message sent if DN doesn’t exist
- Client sends IP to web server to access website
- Website accessed by client
65
Ransomware (definition)
Ransomware holds companies to ransom by encrypting their data and demanding a large sum of money to decrypt it
66
Hackers (definition)
Anyone that attempts to access an IT system without permission
(you can have ethical hackers)
67
Phishing (definition)
Phishing is to attempt to fraudulently gain information by unlawfully making claims via phone/email that the user should share personal/financial details
68
Accidental Damage (4)
- Accidentally delete/overwrite
- Power cut before saving
- Saved in wrong place/name
- Natural Disasters
69
Impacts of Threats on Individuals (4)
- Stress
- Waste Time
- Replace/repair devices
- Could lose photos - sentimental value
70
Impacts of Threats on Organisations (4)
- Loss in business
- Damage to credibility
- Take money + time to fix damages
- Can be viewed as unreliable
71
Reducing Threats to Data (4x2)
File Permissions
- password protection
- allocate right e.g. read-only
Access Levels
- users are given access to files that fulfil their role but nothing more
- fewer people put sensitive files at risk
Passwords
- secret, strong, no key words
- change every 8-12 weeks
Physical Access Control
- don't leave unlocked devices unattended
- biometrics
72
Incremental Back Up (2, Adv:2, Dis:1)
- only back up files that have been changed since the last back up
- nightly/weekly
- doesn't take up much storage
- quicker
- harder to find files to recover
73
Full Back Up (3, Adv:1, Dis:2)
- backs up all files
- weekly/monthly
- out of office hours
- restore files more easily
- expensive
- takes longer
74
Back Up Recovery (2)
- organisation should have formalised plan
- large organisation have a full disaster recovery plan (minimise disruption)
75
LAN and WAN (definition)
Group of connected devices over a:
LAN: small geographical area
WAN: large geographical area
76
Start and Stop Bits (definition)
Start: notifies receiver when data being sent
Stop: notifies when the end of a transmission has been reached
77
Advantages of Proxy Servers (2)
- speeds up access
- more secure (IP hidden from webserver)
78
IPv4 vs IPv6 (2x2)
- IPv4 = 4 sections, binary
- IPv6 = 6 sections, hex
- - 3.4x10^38 IP addresses
79
Router (definition)
Device that forwards packets from one network to another
80
SSH Typical Uses (4)
- Providing secure remoted access for
- - Users/automated processes
- Interactive & automated file transfers
- Issuing remote commands
- Managing network infrastructure
81
FTP 5 Features
- Local computer file manager panel
- - Shows filing structure of local machine
- - When files moved from here to panel 2: uploading from local machine to remote server
- Remote server file manager panel
- - Shows filing structure of remote server
- - When files moved from here to panel 1, downloading files from r.s to l.m
- FTP client to host server connection
- - Connects to remote server
- Status Panel
- - Useful messages from remote server when connected to FTP are reported here
- File Transfer Progress Panel
- - Shows queue of items being down/uploaded
82
Physical Star vs Logical Bus (6)
- Physical Star: layout (cables)
- Logical Bus: data moves
- - data gets broadcasted to all PCs (Hub)
- - receive data -> check if it is yours
- - only 1 broadcast can happen at the same time
- It is possible for a network to have a physical star topology, but logically the data is sent as a bus topology
83
Gateways (2)
- all functions of a router
- + protocol conversions
84
Routers
- connects network to other networks (internet)
- in packet switching:
- - will find most efficient path
- - update NAT table with route
- - packet header: update addresses: MAC + IP of sender + receiver
- will check which link data is to be sent on
